The DUP's chief executive has denied he held a position of seniority over other special advisers (Spads) in the party during the period an overspend in the RHI scheme came to light.

The botched Renewable Heat Incentive (RHI) scheme was set up in 2012 to encourage the burning of eco-friendly wooden pellets, but ran into financial difficulties ahead of its closure in 2016, as it emerged the fuel subsidies offered would result in a £490m overspend to be footed by Northern Ireland's taxpayers.

It comes in written evidence submitted to the RHI Inquiry on Thursday evening by Timothy Johnston, who was appointed to his position as the DUP's top official last year.

Former Enterprise Minister Jonathan Bell has previously alleged before the RHI Inquiry that Mr Johnston pushed for the introduction of cost controls to be delayed, and claimed Mr Johnston held a position at the top of a hierarchy of DUP Spads.

Timothy Johnston has rebuked these suggestion in evidence submitted ahead of his appearance on Friday.

Mr Johnston said all Spads "had access to the First Minister [Arlene Foster]", and he had "no sense that there was an understood or recognised hierarchy of advisers, indeed it was recognised we were answerable to our individual Ministers who themselves regularly interacted".

"I had no involvement in the decision-making processes on the introduction of cost controls in 2015," writes Mr Johnston in his evidence.

Cost controls were introduced for the RHI scheme in August 2015.

Mr Johnston adds he gave advice during a period at the start of 2016 on the process of closing the scheme to new applicants.

On Thursday evening two witness statements were released from Timothy Johnston, as well as a statement from former First Minister Peter Robinson.

In his statement, Mr Robinson said he was not aware of the flaws in the RHI scheme, and only became aware of its flaws through the media after he left office in 2016.

The written evidence from Timothy Johnston and Peter Robinson can be read on the RHI Inquiry website: